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Abstract

Energy confinement time in tokamak à configuration variable (TCV) ohmic L-modes is observed to be strongly dependent on plasma shape. It improves by a factor of 2 as the plasma triangularity is reduced from 0.7 to -0.3 and also improves as the elongation is increased. Local power balance analysis of plasmas where the elongation (1 to 2.6), triangularity (-0.45 to 0.8), current and density were systematically varied has revealed no discernible dependence of the local thermal diffusivity on plasma shape. The changes in global confinement are explained only by a combination of power degradation and geometrical effects. The latter results from a modification in the flux surface separation that affects the temperature gradients and hence the conduction losses. A factor of merit (shape enhancement factor (SEF)) has been defined to quantify this geometrical effect on the global energy confinement. The SEF has been successfully introduced in scaling laws to account for the shape influence. Optimization of the SEF has led to the creation of new configurations with an almost rectangular shape. Current investigations extend this study to conditions with up to 1 MW of eddy current heating (ECH).

Additional information

Authors: MORET J-M, École Polytechnique Fédérale de Lausanne, Centre de Recherches en Physique des Plasmas (CH);BEHN R, École Polytechnique Fédérale de Lausanne, Centre de Recherches en Physique des Plasmas (CH);FRANKE S, École Polytechnique Fédérale de Lausanne, Centre de Recherches en Physique des Plasmas (CH);HOFMANN F, École Polytechnique Fédérale de Lausanne, Centre de Recherches en Physique des Plasmas (CH);POCHELON A, École Polytechnique Fédérale de Lausanne, Centre de Recherches en Physique des Plasmas (CH);WEISEN H, École Polytechnique Fédérale de Lausanne, Centre de Recherches en Physique des Plasmas (CH)
Bibliographic Reference: Article: Bulletin of the American Physical Society, Vol. 42 (1997) No. 10, p.1857
Record Number: 199810132 / Last updated on: 1998-02-12
Category: PUBLICATION
Original language: en
Available languages: en
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